#include <stdio.h>
#include <pthread.h>
#define     BUFFER_SIZE     16  //缓冲区数量
struct prodcons
{
    int buffer[BUFFER_SIZE];    //实际数据存放的数组
    pthread_mutex_t lock;       //互斥体lock用于对缓冲区的互斥操作
    int readpos, writepos;      //读写指针
    pthread_cond_t notempty;    //缓冲区非空的条件变量
    pthread_cond_t notfull;     //缓冲区未满的条件变量
};
//初始化缓冲区结构
void init(struct prodcons *b)
{
    pthread_mutex_init(&b->lock, NULL);
    pthread_cond_init(&b->notempty, NULL);
    pthread_cond_init(&b->notfull, NULL);
    b->readpos = 0;
    b->writepos = 0;
}
//将产品放入缓冲区，这里是存入一个整数
void put(struct prodcons *b, int data)
{
    pthread_mutex_lock(&b->lock);
    //等待缓冲区未满
    if ( (b->writepos + 1) % BUFFER_SIZE == b->readpos )
    {
        pthread_cond_wait(&b->notfull, &b->lock);
    }
    //写数据，并移动指针
    b->buffer[b->writepos] = data;
    b->writepos++;
    if ( b->writepos >= BUFFER_SIZE )
        b->writepos = 0;
    //设置缓冲区非空的条件变量
    pthread_cond_signal(&b->notempty);
    pthread_mutex_unlock(&b->lock);
}
//从缓冲区中取出整数
int get(struct prodcons *b)
{
    int data;
    pthread_mutex_lock(&b->lock);
    //等待缓冲区非空
    if ( b->writepos == b->readpos )
    {
        pthread_cond_wait(&b->notempty, &b->lock);
    }
    //读数据，移动读指针
    data = b->buffer[b->readpos];
    b->readpos++;
    if ( b->readpos >= BUFFER_SIZE )
        b->readpos = 0;
    //设置缓冲区未满的条件变量
    pthread_cond_signal(&b->notfull);
    pthread_mutex_unlock(&b->lock);
    return data;
}
//测试：生产者线程将1到10000的整数送入缓冲区，消费者线程从缓冲区中获取整数，两者都打印信息
#define     OVER    ( - 1)
struct prodcons buffer;
void *producer(void *data)
{
    int n;
    for ( n = 0; n < 10000; n++ )
    {
        printf("%d ----->\n", n);
        put(&buffer, n);
    }
    put(&buffer, OVER);
    return NULL;
}
void *consumer(void *data)
{
    int d;
    while ( 1 )
    {
        d = get(&buffer);
        if ( d == OVER )
            break;
        printf("---->\n", d);
    }
    return NULL;
}
int main()
{
    pthread_t th_a, th_b;
    void *retval;
    init(&buffer);
    //创建生产者和消费者线程
    pthread_create(&th_a, NULL, producer, 0);
    pthread_create(&th_b, NULL, consumer, 0);
    //等待两个线程结束
    pthread_join(th_a, &retval);
    pthread_join(th_b, &retval);

    return 0;
}
